Rigging Non-spherical eyes in 2.79 or 2.8 that will work in Unity
Duplicate eye rotate and rename it to TrackToBone. Parent it to the parent of eye scale. (For this test setup, it won't need a parent.) Leave the track to constraint on TrackToBone as it was.

Add a Copy Rotation Constraint to the eye rotate with the TrackToBone the target. Choose Local Space for both inputs.



The TrackToBone will do the tracking and the eye rotate bone will copy it's rotation in the local (deformed) space.